SWCNTs@GQDs composites as nanocarriers for enzyme-free dual-signal amplification electrochemical immunoassay of cancer biomarker.

Carcinoembryonic antigen (CEA) as a typical biomarker plays a remarkable role in various human physiological processes. A sensitive and rapid method should be developed to realize the precise diagnosis of cancer at its early stage. In this work, we successfully synthesized the peroxidase-like graphene quantum dots (GQDs) and utilized it to fabricate an enzyme-free electrochemical immunosensor towards CEA by forming a single-wall carbon nanotubes@GQDs (SWCNTs@GQDs) composite. In addition to the SWCNTs@GQDs, reduced graphene oxide-Au nanoparticles (rGO-Au NPs) with the huge specific surface area and excellent conductivity were employed to modify the electrodes, leading to a dual-signal amplification result. Both the electrochemical impedance spectroscopy and cyclic voltammetry measurements were performed to evaluate the interface properties of the layer-by-layer modified electrodes. The proposed electrochemical immunosensor displayed a good specificity and sensitivity towards the detection of CEA ranging from 50 pg mL to 650 pg mL with a low detection limit of 5.3 pg mL. This simple and inexpensive immunosensor shows promising potential for the determination of other biomarkers in clinical translation.